Around six weeks after joining up with the 17th Service Battalion Welsh Regiment in July 1916, Lloyd was wounded in the leg and hand leading an attack in the Battle of Mametz.

Because of intense enemy shelling, it took colleagues 13 hours to reach him and take him to a dressing station.

This was a time when German agents were working hard abroad, organising the so-called “Black Tom” explosion on July 30, 1916, in Jersey City, New Jersey, an act of sabotage on American ammunition supplies to prevent them being used by the Allies in World War One.

They also flooded European and foreign newspapers with news of German victories.

So Britain fought back with its own secret units, including MI7, to handle foreign and domestic propaganda.

It was into this unit into the recuperating Lloyd, then a lieutenant, was recruited, alongside AA Milne, the author of Winnie the Pooh.

Mr Arter said: “They asked people like Uncle Jim and AA Milne to write press articles about their war experiences with a view to getting them printed around the world.”

The eldest son of the Rev JH Lloyd of Aberedw, Builth Wells, and born in Talley, near Llandeilo, James Lloyd would go on to found Craig y Nos Preparatory School in Swansea in 1920 with his brother, John, apparently thrilling pupils by showing them the bullet which injured him at Mametz.

His classics training helped him write about his experiences.

At the time, this work was regarded as “highly sensitive” and all official records and documents of MI7 – set up during World War One to work in the fields of propaganda and censorship – were later destroyed.

Mr Arter, who found the documents at home in Hereford, said: “The reason his archive was not destroyed was because he took examples home – strictly against policy, of course!”

James “Jim” Lloyd died in Swansea on January 27, 1955, aged 64. He is now buried in a churchyard in Penllergaer.

Mr Arter said: “I found around 150 articles by my uncle while I was clearing out some papers on a wide range of subjects.

“Some deal with his experiences in the frontline trenches, others describing, for example, raiding parties, the air war and the importance of aeroplanes, pigeons, and balloons on the Western Front.

“Others deal with titles such as German methods in Belgium.”

Mr Arter said the entire archive is now to be hosted by the 1914-19 Europeana Website so that anyone will be able to freely access and study the documents.

He said: “I hope the original documents themselves will be kept in Wales. I am hoping a museum or some other institution will be prepared to accept them and make them available for public access and study.”

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